Cadmium-induced heme oxygenase-1 gene expression is associated with the depletion of glutathione in the roots of Medicago sativa
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Following previous findings that cadmium (Cd) induces heme oxygenase-1 (HO1) gene expression in alfalfa seedling roots, we now show that the decreased glutathione (GSH) and ascorbic acid (AsA) contents, induction of HO-1 gene expression and its protein level by Cd was mimicked by a GSH depletor diethylmaleate (DEM). Meanwhile, above Cd- or DEM-induced decreased GSH content followed by HO-1 up-regulation could be strengthened or reversed differentially by the application of a selective inhibitor of GSH biosynthesis l-buthionine-sulfoximine (BSO), or exogenous GSH and AsA, respectively. The antioxidative behavior of HO-1 induction was further confirmed by histochemical staining for the detection of loss of membrane integrity in a short period of treatment time. Additionally, the induction of HO-1 transcript was inhibited by the transcriptional inhibitor actinomycin D (ActD) or protein synthesis inhibitor cycloheximide (CX, especially). In contrast, the level of HO-2 transcript did not change upon various treatments. Together, above results suggested that Cd-induced up-regulation of HO-1 gene expression is associated with GSH depletion, which is at least existing transcriptional regulation level, thus leading to enhanced antioxidative capability transiently.
KeywordsAlfalfa seedling roots Ascorbic acid Cd-induced oxidative stress Glutathione depletion HO-1 gene expression
This work was supported by the Program for New Century Excellent Talents in University (grant no. NCET-07-0441 to W.S.), the National Natural Science Foundation of China (grant no. 30971711 to W.S.), and the Fundamental Research Funds for the Central Universities (grant no. KYZ200905 to W.S.). We also thank Dr. Evan Evans from the University of Tasmania, Australia, for his kind help in writing the manuscript.
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